Windows XP shutting down

I have Windows XP SP3,and it just crashes and shuts down.I don’t know why does it happen but could it be maybe because of overheating or something else?I don’t think it is virus(scanned it with AVG and nothing has been found)..?
Answer #1
AVG is not good enough to check for infections. Get a decent AV and use HWMonitor to measure temperatures.
Answer #2
Does it shut down or blue screen? Temps? What does it say in the event log? Control > Admin tools > Event viewer
Answer #3
crashes only one time? or every time? if One time then ignore it.
Answer #4
is it a blank screen or BSOD?
Answer #5
Also good to let us know what you were doing at the time of crash, is it random or only specific apps?
Answer #6
Probably over heating the cpu , pull the fan of the cpu out and blow out the dust and fluff built up in the cooling grills between the fan and cpu ,,,, see how that goes , I have a machine that random shutdowns and thats what it is with it , every few mths I got to clean it out and it runs fine again .
Answer #7
http://www.technibble.com/how-to-disable-automatic-restart-for-bsod-if-you-are-unable-to-get-into-windows/
Right Click on “My Computer” and goto “Properties”. Then goto the “Advanced” tab and under the headline “Startup and Recovery”, press the “Settings” button. Untick the “Automatically Restart” box and press Ok.
This enable the Blue Screen Of Death , since windows xp they switch to automatic reboot on failure.
At least now if you have a problem , you’ll get a blue screen of death telling you what’s the problem.